August 7, 2021
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Perhaps you’ve heard the terms “raster” and “vector” before when discussing which images to use for your next big project. Whether you’re a designer editing an image or a customer looking for a compelling photo, knowing the difference between a raster and a vector graphic can save you time and money down the road. So what’s the difference between these two terms? Let’s break them down in further technical detail below.
A raster image or raster file is one you know rather well, even if you don’t think you know it due to its name. In reality a raster file is simply an image or a file that’s composed of pixels. Any picture you take with a camera or any image that has already been printed is a raster image.
But what does this mean exactly? Well, if you were to examine an image by zooming into it, you’d see that the image itself is composed of pixels, each one representing one square of color, working together to create a larger image. The more pixels in any given area, the larger the image can be printed and look sharp because it will have a higher pixel density. For instance, if we examined one square inch of a picture and saw that there were 300 pixels in that square inch, we could then compare it to another image with 1,000 pixels in one square inch. From this we’d find that the picture with 1,000 pixels per inch possesses a greater quality at that size.
This is why some images appear to be blurry and pixelated while others appear crisp. If the image is pixelated or blocky, it’s because there are less pixels per inch (PPI or DPI for dots per inch). Whenever you go to your favorite stock photo site and see PPI or DPI, now you’ll know exactly what that means.
At the end of the day, you need only remember that a raster image can only get so big before the quality starts to deteriorate. The more you stretch an image, the uglier it will look because the pixels are growing in size but not in number. If an image with 300 PPI that’s 10 inches wide is stretched to 20 inches wide, the PPI will actually be cut in half to 150 PPI, making it extremely pixelated and therefor visually blurry or choppy.
Use the handy metrics below to determine the standard PPI for each imaging format.
Hi resolution screen – 150 ppi
Standard resolution screen – 72 ppi
Raster images are best used for photos, plain and simple. Whether you’re printing a photo or sharing one on social media, the colors are properly represented by the transitioning pixels.
.jpg (Joint Photographics Expert Group)
.png (Portable Network Graphic)
.gif (Graphics Interchange Format)
.bmp (Bitmap Image File)
.pdf (Portable Document Format, can be vector too)
.tiff (Tagged Image File Format)
.psd (Adobe Photoshop Document)
A vector image is one made of pathways and curves that are determined by mathematical formulas via computer. While there’s math behind the image, you won’t need to know much more than that solely because your computer is doing all the work, as it knows where the lines are and what the curves will look like.
But perhaps the very best part about a vector image is that, unlike a raster image, you can increase the size as much as you like without worrying about how it will look. If your original image could fit on a sheet of printer paper, a resized version of the same image as tall as the Empire State Building would still look the very same. There are no pixels involved and therefore no need to worry about overall quality.
Just as there’s a time and place to use raster, so too is there a time and place for vector. Because a vector image can be resized without end, designers and printers love these files the most. Often you’ll find that logos, icons, and computer-generated illustrations are vector images because they need to be reused and resized for different purposes. A logo may sit in the header of a company letter, or it may be used on the side of a commercial vehicle. This in-turn saves time and money along the way because new images don’t need to be produced over and over again.
.pdf (Portable Document Format, saved via from vector programs)
.ai (Adobe Illustrator document)
.eps (Encapsulated PostScript)
.svg (Scalable Vector Graphic)
Determining whether your project requires a raster or vector image can be confusing at times. As soon as you’ve come to understand the ins and outs of this process, exceptions to the rules will arise as they often do. If you find yourself in need of help, contact the experts at Rhino Digital to walk through the process together. From there we’ll decide the best course of action for your needs, and put the materials in your hand to ensure your project runs according to plan.